P0300 - Random multiple misfire. So it is something that can cause a lean or rich condition that is enough to cause cylinders to misfire.
A vacuum leak can do that, so can low fuel pressure. Low fuel pressure will also cause a severe loss of power.
I would start by measuring the fuel pressure, you should have between 50 and 60 psi with the key on engine off. When you turn the key off it should hold that pressure for a while (ideally it will hold forever without any leakage, but they all leak a bit).
Also, look for a broken or cracked vacuum line, these can be hidden in places like the brake booster or even in the EVAP lines.
The easiest way to determine if it is a vacuum leak is to look at the fuel trims with a scan tool and see what they do as you raise the rpm's.
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Saturday, June 2nd, 2018 AT 8:59 PM